The invention relates to an apparatus for temperature calibration of temperature sensors, comprising a housing unit containing at least one dry block having a cavity for receiving a sensor-receiving liner, and a heating/cooling means for the provision of an accurate temperature of the dry block.
Further, the invention relates to a liner for use in such an apparatus.
As components and equipment age, and also are subjected to temperature changes and mechanical strains, the critical capacity will decrease. This is called drift. When this happens, one can no longer rely on previous capacity tests, and this may result in a poorer quality in development and production. Since one can not prevent drift, one must instead detect and eliminate the effect thereof by means of calibration.
As known, calibration is to compare the capacity of an equipment with a known standard. The standards are maintained by national and international accredited calibration laboratories.
Today, there are imposed aggravated demands on the industry with respect to measuring accuracy and quality assurance (ISO 9000), and there is then required calibrating equipment which satisfies the requirement of today and complies with the new standards within temperature calibration.
The known devices for calibration of temperature sensors generate an accurate temperature in a portable unit which can be operated equally simple out on the topical installation as in on the laboratory. Even if temperature calibrators according to the prior art are very accurate and accepted, they are today utilizing equipment which is relatively space demanding and expensive in purchase, and which requires a long time for temperature stabilization.
The known devices of the topical type are based on the use of a dry block having a cavity for receiving a liner or sleeve in the form of a massive body which is provided with a central, elongated cavity for introduction of the topical temperature detector or sensor to be calibrated. The elongated cavity is adapted for accurate reception of the topical sensor, to secure an accurate temperature and a correct calibration, and thus is limited to calibration of sensors having the correct dimensions.
There also exist liquid-based temperature calibrators with a housing unit having a recess which, in use, can be filled with a liquid to form a liquid bath for submersion of the temperature sensor to be calibrated. However, such a calibrator must be emptied of liquid and possibly be cleaned for each use, and in order to be able to be transported, and thus is not so easy and practical to use as desired.
It is an object of the invention to provide a temperature calibration apparatus which will give dry block calibrators an extended field of use by being able to calibrate a wider spectrum of temperature detectors or sensors, and which simultaneously secure a more accurate and more stable calibration.
A further object of the invention is to provide a liner giving substantial advantages of use when utilized in such an apparatus.
For the achievement of the above-mentioned objects there is provided an apparatus of the introductorily stated type which, according to the invention, is characterized in that at least one sensor-receiving liner is a cylindrical body which is adapted to the dry block cavity and is arranged to be filled with a heat transferring liquid.
An advantageous embodiment of the apparatus is characterized in that the liner body is a container which is open at one end, the open end being provided with a cap for closing of the container. With this embodiment the liquid-filled liner can be transported without one having to pour out the liquid.
According to the invention there is also provided a liner for use in an apparatus for calibration of temperature sensors, wherein the liner is adapted to be placed in a cavity in a dry block in the apparatus and is arranged to receive at least one sensor to be calibrated, which liner is characterized in that it has a cavity which is adapted to receive a heat transferring liquid and one or more sensors in the liquid-filled cavity.
In the apparatus according to the invention a standard dry block liner is replaced by a liquid-filled liner, and consequently one combines a dry block calibrator and a liquid bath calibrator in one and the same unit. The invention gives a liquid-based temperature calibrator a mobility and a combination possibility which do not exist today. The liquid-filled liner can be placed in the same cavity or hole in the housing unit as that which is today used for the placing of standard sensor-receiving liners. By means of the apparatus according to the invention liquid temperature calibration is carried out in the field outside of the laboratories, and the apparatus enables a simpler and more accurate calibration of temperature sensors.